In this work the parameter a representing the decay-rate of luminescence signal was investigated for two different samples, for luminescence dating purpose. The procedures of preheating/measurement and dose/preheating/ measurement were repeatedly used for the natural and beta-irradiated forms of the samples at different infrared-stimulation time. Experimental data has shown that the IRSL signal decays in a way, which depends on the beta-dose given to the samples. This behavior is different from that observed by DULLER1 who did not find such dose-dependence. © 2005 Akadémiai Kiadó.